/**
    Add a renderer to a hierarchy passed as parameter.
 */
 static
 public
 void addRenderer(RendererSupport repository, String renderedClassName,
	   String renderingClassName) {
   LogLog.debug("Rendering class: ["+renderingClassName+"], Rendered class: ["+
	 renderedClassName+"].");
   ObjectRenderer renderer = (ObjectRenderer)
            OptionConverter.instantiateByClassName(renderingClassName,
					    ObjectRenderer.class,
					    null);
   if(renderer == null) {
     LogLog.error("Could not instantiate renderer ["+renderingClassName+"].");
     return;
   } else {
     try {
Class renderedClass = Loader.loadClass(renderedClassName);
repository.setRenderer(renderedClass, renderer);
     } catch(ClassNotFoundException e) {
LogLog.error("Could not find class ["+renderedClassName+"].", e);
     }
   }
 }
 

/**
 * 获取资源文件的绝对路径
 * 
 * @param file
 * @return
 */
public static URL getResourceFileUrl(String file) {
	if(file == null) return null;
	
	URL url = Loader.getResource(file);
	if (url == null) {
		url = ClassLoader.class.getResource(file);
	}
	return url;
}
 

private
 void readLevel(ObjectInputStream ois)
                     throws java.io.IOException, ClassNotFoundException {

   int p = ois.readInt();
   try {
     String className = (String) ois.readObject();
     if(className == null) {
level = Level.toLevel(p);
     } else {
Method m = (Method) methodCache.get(className);
if(m == null) {
  Class clazz = Loader.loadClass(className);
  // Note that we use Class.getDeclaredMethod instead of
  // Class.getMethod. This assumes that the Level subclass
  // implements the toLevel(int) method which is a
  // requirement. Actually, it does not make sense for Level
  // subclasses NOT to implement this method. Also note that
  // only Level can be subclassed and not Priority.
  m = clazz.getDeclaredMethod(TO_LEVEL, TO_LEVEL_PARAMS);
  methodCache.put(className, m);
}
PARAM_ARRAY[0] = new Integer(p);
level = (Level) m.invoke(null,  PARAM_ARRAY);
     }
   } catch(Exception e) {
LogLog.warn("Level deserialization failed, reverting to default.", e);
level = Level.toLevel(p);
   }
 }
 

private
MDC() {
  java1 = Loader.isJava1();
  if(!java1) {
    tlm = new ThreadLocalMap();
  }
}
 

/**
    Used internally to parse a layout element.
 */  
 protected
 Layout parseLayout (Element layout_element) {
   String className = subst(layout_element.getAttribute(CLASS_ATTR));
   LogLog.debug("Parsing layout of class: \""+className+"\"");		 
   try {
     Object instance 	= Loader.loadClass(className).newInstance();
     Layout layout   	= (Layout)instance;
     PropertySetter propSetter = new PropertySetter(layout);
     
     NodeList params 	= layout_element.getChildNodes();
     final int length 	= params.getLength();

     for (int loop = 0; loop < length; loop++) {
Node currentNode = (Node)params.item(loop);
if (currentNode.getNodeType() == Node.ELEMENT_NODE) {
  Element currentElement = (Element) currentNode;
  String tagName = currentElement.getTagName();
  if(tagName.equals(PARAM_TAG)) {
           setParameter(currentElement, propSetter);
  } else {
         parseUnrecognizedElement(instance, currentElement, props);
     }
}
     }
     
     propSetter.activate();
     return layout;
   }
   catch (Exception oops) {
     LogLog.error("Could not create the Layout. Reported error follows.",
	   oops);
     return null;
   }
 }
 

/**
    Used internally to parse a level  element.
 */
 protected
 void parseLevel(Element element, Logger logger, boolean isRoot) {
   String catName = logger.getName();
   if(isRoot) {
     catName = "root";
   }

   String priStr = subst(element.getAttribute(VALUE_ATTR));
   LogLog.debug("Level value for "+catName+" is  ["+priStr+"].");
   
   if(INHERITED.equalsIgnoreCase(priStr) || NULL.equalsIgnoreCase(priStr)) {
     if(isRoot) {
LogLog.error("Root level cannot be inherited. Ignoring directive.");
     } else {
logger.setLevel(null);
     }
   } else {
     String className = subst(element.getAttribute(CLASS_ATTR));      
     if(EMPTY_STR.equals(className)) {	
logger.setLevel(OptionConverter.toLevel(priStr, Level.DEBUG));
     } else {
LogLog.debug("Desired Level sub-class: ["+className+']');
try {	 
  Class clazz = Loader.loadClass(className);
  Method toLevelMethod = clazz.getMethod("toLevel", 
					    ONE_STRING_PARAM);
  Level pri = (Level) toLevelMethod.invoke(null, 
					    new Object[] {priStr});
  logger.setLevel(pri);
} catch (Exception oops) {
  LogLog.error("Could not create level ["+priStr+
	       "]. Reported error follows.", oops);
  return;
}
     }
   }
   LogLog.debug(catName + " level set to " + logger.getLevel());    
 }
 

/**
    Used internally to parse an appender element.
  */
 protected
 Appender parseAppender (Element appenderElement) {
   String className = subst(appenderElement.getAttribute(CLASS_ATTR));
   LogLog.debug("Class name: [" + className+']');    
   try {
     Object instance 	= Loader.loadClass(className).newInstance();
     Appender appender	= (Appender)instance;
     PropertySetter propSetter = new PropertySetter(appender);

     appender.setName(subst(appenderElement.getAttribute(NAME_ATTR)));
     
     NodeList children	= appenderElement.getChildNodes();
     final int length 	= children.getLength();

     for (int loop = 0; loop < length; loop++) {
Node currentNode = children.item(loop);

/* We're only interested in Elements */
if (currentNode.getNodeType() == Node.ELEMENT_NODE) {
  Element currentElement = (Element)currentNode;

  // Parse appender parameters 
  if (currentElement.getTagName().equals(PARAM_TAG)) {
           setParameter(currentElement, propSetter);
  }
  // Set appender layout
  else if (currentElement.getTagName().equals(LAYOUT_TAG)) {
    appender.setLayout(parseLayout(currentElement));
  }
  // Add filters
  else if (currentElement.getTagName().equals(FILTER_TAG)) {
    parseFilters(currentElement, appender);
  }
  else if (currentElement.getTagName().equals(ERROR_HANDLER_TAG)) {
    parseErrorHandler(currentElement, appender);
  }
  else if (currentElement.getTagName().equals(APPENDER_REF_TAG)) {
    String refName = subst(currentElement.getAttribute(REF_ATTR));
    if(appender instanceof AppenderAttachable) {
      AppenderAttachable aa = (AppenderAttachable) appender;
      LogLog.debug("Attaching appender named ["+ refName+
		   "] to appender named ["+ appender.getName()+"].");
      aa.addAppender(findAppenderByReference(currentElement));
    } else {
      LogLog.error("Requesting attachment of appender named ["+
		   refName+ "] to appender named ["+ appender.getName()+
               "] which does not implement org.apache.log4j.spi.AppenderAttachable.");
    }
  } else {
         parseUnrecognizedElement(instance, currentElement, props);
     }
}
     }
     propSetter.activate();
     return appender;
   }
   /* Yes, it's ugly.  But all of these exceptions point to the same
      problem: we can't create an Appender */
   catch (Exception oops) {
     LogLog.error("Could not create an Appender. Reported error follows.",
	   oops);
     return null;
   }
 }